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DNS/DHCP configuration help

Posted on 2009-04-09
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Last Modified: 2012-05-06
Ok, I have inherited the job of managing DNS/DHCP and I am trying to figure it all out. I have some understanding of how they work, and everything humming along, but the problem is, it is messy. Our Reverse lookup in DNS has a lot of junk in it. Our Forward lookup zone looks a bit better. DHCP seems ok. However, stale records in DNS are causing systems that get renamed or added or moved on the network to not show up right away. That, in turn, causes some issues with some local apps that require DNS to be resolving properly for the app to run right.

I have been looking at our scavenging and aging settings, along with the Refresh and No Refresh settings. I think they need some tweaking. However, I want to make sure I do not cause any disruptions in the process of trying to get DNS cleaned up and running smoothly.

We have 3 DC's for DNS, The DC is set for a refresh and no refresh of 7 days and 7 days. The forward lookup zone is set for 12 hour no resfresh, 4 hour refresh. Reverse lookup is set for 3.5 days on both refresh and no refresh.

Scavenging is turned off I guess. I want to turn it on, but I think the settings need tweaking so that the systems resolve properly when all the stale records are cleaned out. My fear is that many of the records, like 75% or more are stale and that when scavenging occurs, it will clean it all out.

Any and all guidance is appreciated. I have been digging and searching a ton and am just at my wits end.

Thanks in advance.
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Question by:pprintzQCC
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Chris Dent earned 2000 total points
ID: 24136051

> The forward lookup zone is set for 12 hour no resfresh, 4 hour refresh

This is much too short.

The minimum that you should consider for the Refresh Interval is 24 hours. These are the registration intervals that you must try to work with:

 - Clients with Static IP Addresses (Servers, etc) - Registration occurs via the DHCP Client Service. Default Refresh is once every 24 hours.
 - Clients with DHCP IP Addresses - Registration occurs via the DHCP Server by default. Default Refresh is once on lease creation, and once 50% of the way through the lease. If update via DHCP is disabled then updates occur with the same frequency as clients with static IP addressing.
 - Domain Controllers - Registration of Service Records occurs via the NetLogon Service. Default Refresh is once every 24 hours.

It is possible to find out which records will be Scavenged based on current, or projected Refresh and No-Refresh values. I cover a few methods in my blog here:

http://www.highorbit.co.uk/?p=199

I advise you fix the Refresh Interval first though. What is the Lease duration configured on your DHCP server?

Chris
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